Time-correlated structure in spin fluctuations in pulsars

We study statistical properties of stochastic variations in pulse arrival times, timing noise, in radio pulsars using a new analysis method applied in the time domain. The method proceeds in two steps. First, we subtract low-frequency wander using a high-pass filter. Secondly, we calculate the discrete correlation function of the filtered data. As a complementary method for measuring correlations, we introduce a statistic that measures the dispersion of the data with respect to the data translated in time. The analysis methods presented here are robust and of general usefulness for studying arrival time variations over time-scales approaching the average sampling interval. We apply these methods to timing data for 32 pulsars. In two radio pulsars, PSRs B1133+16 and B1933+16, we find that fluctuations in arrival times are correlated over time-scales of 1020?d with the distinct signature of a relaxation process. Though this relaxation response could be magnetospheric in origin, we argue that damping between the neutron star crust and interior liquid is a more likely explanation. Under this interpretation, our results provide the first evidence independent from pulsar spin glitches of differential rotation in neutron stars. PSR B0950+08 shows evidence for quasi-periodic oscillations that could be related to mode switching.

Title	Time-correlated structure in spin fluctuations in pulsars
Creator	Link, B.
	Price, S.
	Nice, David J.
	Shore, S. N.
Publisher	Monthly Notices of the Royal Astronomical Society
Academic Department	Physics
Division	Natural Sciences
Organization	Lafayette College
Date Issued	November 2012
Date Available	2013-02-26T15:38:11Z
Type	Article
Language	English
Keyword	dense matter
	methods: data analysis
	pulsars: general
	stars: interiors
	stars: rotation
	stars: neutron
Bibliographic Citation	Price, S., et al. (2012) "Time-correlated structure in spin fluctuations in pulsars." Monthly Notices of the Royal Astronomical Society 426: 2507–2521.
Standard Identifier	Handle 10385/1120
Standard Identifier	DOI 10.1111/j.1365-2966.2012.21863.x
Permalink	http://hdl.handle.net/10385/1120
Rights Statement	In Copyright
Rights Holders	Link, B.
	Price, S.
	Nice, David J.
	Shore, S. N.